1. Field of the Invention
This invention pertains to clamps generally, and particularly to locking clamps useful for vehicle hitch receivers and other similar apparatus to prevent motion or rattling.
2. Description of the Related Art
Passenger vehicles are well adapted to transport people, as they were designed to do, and will readily transport small cargo such as grocery sacks and briefcases. People, however, do not always choose to rely upon passenger vehicles for transportation. During outings, such as week-end trips, vacations or competitions, other modes of transportation are often desired. Skis, canoes or bicycles may be integral to the outing. The recreational enthusiast knows the value of quiet leisure away from the hustle and bustle of the city, but must somehow find a way to carry both passengers and additional transportation equipment to the place of leisure. The competitor must get to and from the competitions, and will want to preserve the equipment for competition.
The method of transporting equipment should not detract from the goal of the outing, be it leisure or competition, nor should it cause any damage to the passenger vehicle. Unfortunately, in the past these simple goals have each been contrary to each other. A multitude of roof-top racks and carriers have been designed for either permanent or temporary mounting. These carriers are usually designed and manufactured to be compatible with one or a limited number of vehicles, since each vehicle is sized and shaped uniquely.
While the permanent variety usually are more reliable in load carrying, they are also usually installed at the factory to carefully control installation and thereby prevent any leakage or damage which might otherwise occur. Moreover, they permanently add to the size of the vehicle, and also generally detract from the vehicle's appearance.
Temporary carriers have been designed from diverse materials and geometries, including materials such as foam block, foam pad, rubber, plastic, metal and wood. To reduce the inventory required by a vendor to sell the temporary carrier, common vehicle features are used to attempt to provide the necessary support for cargo. For example, gutters are often found around vehicle doors, and a number of carriers clamp onto these gutters. Unfortunately, not all vehicles have features such as gutters, and so several different carriers must still be designed. Other carriers rely on the roof of the vehicle to provide both load bearing and also a place for friction, suction or magnetic grab. These temporary carriers have a tendency to be more temporary than planned or desired, occasionally allowing the cargo to slip and either be damaged or damage the vehicle. Such an event is totally unacceptable and will render a carrier useless.
In addition to the other challenges, roof-top carriers present an obstacle during loading and unloading. The equipment must somehow be placed on top of the vehicle without damaging either the vehicle or the equipment. Yet, the reason the equipment is being placed on top of the vehicle is because of large size and/or great bulk.
Other prior art carriers have been designed to mount on the bumper of a vehicle. While this type of carrier is often easier to load and unload, the limitations related to different vehicle designs found with the roof top carriers are still present. Different vehicles have different bumper designs. Some of the most modem vehicles offer no access to the bumper at all, and so different carriers must still be designed and stocked to accommodate different vehicles.
Given the limitations of the prior art, it is not surprising that there has been a relative explosion in carriers designed to install directly into a hitch receiver. The hitch receiver acts as a universal coupling into which trailer balls for utility and boat trailers may be attached, and the hitch receiver may also be used to directly support a carrier. Like the bumper carrier, a hitch receiver carrier provides the advantage of easy equipment loading. In addition, hitch receivers have become standard to several sizes, two sizes in particular being the most common. The large size, a two inch receiver, is designed for high loads and may be specified, for example, for trailers as large as 3,500 pounds and tongue weights as great as 350 pounds. For smaller loads, typically up to 2,000 pounds and tongue weights of 200 pounds, a one and one-quarter inch hitch receiver is used.
While the hitch receiver designs have vastly eased the problems of different vehicle designs, there are still limitations therein that manufacturers have not been able to satisfactorily address. One limitation is the variability of the receiver opening and the hitch outer dimensions, which should desirably fit tightly within the receiver opening.
Another problem with hitch receiver carriers is when they support relatively large loads. The carrier is on a long arm extending from the receiver. When acceleration occurs in a vertical direction, the receiver is carrying the load exactly as it was designed for. Unfortunately, events such as acceleration, bumps and cornering lead to forces which are not always directly vertical. Particularly with the long vertical arm, forces transverse to the vehicle are amplified at the hitch. The carrier may sway or pivot undesirably within the receiver.
The carrier may also rattle or chatter within the receiver. This may occur when a carrier is installed in the hitch receiver, or may even occur if a trailer ball is placed therein. The hitch receiver coupling by nature must be an imperfect fit that allows relative motion between the hitch receiver and a hitch or trailer ball shank, so that the hitch or shank may be inserted into the receiver and removed therefrom. The need for an imperfect fit also means a loose fitting which is prone to chatter and rattling, which although not normally detrimental to performance, is annoying.
Finally, there are two different standard receiver sizes that must be accommodated. When a trailer ball shank or carrier is designed for the one and one-quarter inch receiver, it heretofore could not be used on the two inch receiver, since the quantity of motion relative to the receiver would be destructive.
One prior art anti-rattle device for use on a hitch receiver is illustrated in U.S. Pat. No. 5,593,172 to Breslin, the contents and appropriate teachings which are incorporated herein by reference. Breslin discloses a square collar having a number of screw holes therein. The collar is of sufficient diameter to fit around the hitch receiver and hitch. Screws that pass through some of the screw holes provide clamping forces to the hitch receiver, and the collar is designed to be a relatively permanent attachment to the hitch receiver. Each time a hitch is inserted into the hitch receiver, a special hand adjustment screw is tightened to press against the hitch and thereby force the hitch against the hitch receiver.
The Breslin device is limited in several important aspects. The many screws and screw holes illustrated by Breslin are costly, time consuming, and, due to their size and quantity, easy to lose during shipping and storage. In operative state, the increasing numbers of screws will also increase the likelihood that one of the screws will loosen or fail during operation, due to manufacturing tolerances and other factors, such as greater variability in torques applied to each screw. The small screws may readily be stripped either at the threaded shaft or at the screw head, making it difficult and undesirable to change the collar from one hitch receiver to another. Finally, the maximum force that may be applied through the Breslin design is determined directly by the torque applied at the screw, which may not be sufficient in all instances, or, as aforementioned, may lead a user to attempt to apply too much torque and thereby accidentally destroy the screw threads or screw head.
The prior art limitations on adaptability are particularly apparent when several different types of hitches or hitch receivers may be encountered. For example, a vehicle may have a two inch receiver and need to attach therein a two inch carrier and a one and one-quarter inch trailer ball shank. Each should fit tightly within the two inch receiver and not rattle, wear or require any significant screwing or clamping to make the different combinations work. Furthermore, more than one vehicle may be equipped with a hitch receiver, and each of the combinations of hitches and carriers should likewise be readily interchangeable between vehicle receivers.